A. Field of the Invention
The invention relates to the field of optical communications and particularly to solid state sources of light for use in fiber optical communication systems.
B. Description of the Prior Art
Efficient fiber optical communication requires a light source having high speed, high external quantum efficiency, and high source-to-fiber coupling efficiency in a package which is mechanically stable and readily mated to the fiber or fiber bundle. Prior attempts to meet such requirements have not been completely successful. Conventional GaAs light emitting diodes have not achieved high efficiency because of self-absorption of the generated light in the absorbing GaAs substrate. To decrease such self-absorption, the prior art has utilized the "Burrus etched-well" structure in which the absorbing GaAs substrate is simply etched away. While such structure does improve external efficiency, the resulting device is too fragile to be useful in a practical system.
To overcome the problem of low efficiency or fragile GaAs devices, diodes have also been fabricated using amphoterically doped Si diodes. While these Si diodes are efficient, they are notoriously slow (bandwidths less than 1 MHz). Unfortunately, the physical process (shallow, donor-deep acceptor pair recombination) resulting in the high efficiency device necessarily is accompanied by a relatively long radiative lifetime. Thus, amphoteric Si doped devices are unsuitable for most optical fiber communication systems.